The underwater neutrino telescope NT-200 is located
in the Siberian lake Baikal at a depth of approximately 1 km. Deployment
and maintenance of the Baikal detector is carried out during the winter
months, when the lake is covered with a thick ice sheet. From the ice surface,
the optical sensors can easily be lowered into the water underneath. Once
deployed, the optical sensors take data over the whole year and the data
taken are permanently transmitted to the shore over electrical cables.

The BAIKAL experiment played a pioneering role in neutrino
astronomy: During spring 1993, scientists from Russian institutes and from
DESY were the first to install an underwater telescope which took data
not only for some hours, but for a whole year. At that time, the detector
comprised only three strings carrying 36 optical sensors in total. Since
1998 the Baikal collaboration takes data with the NT-200 telescope which
consists of 192 optical sensors deployed on eight strings.

DESY Zeuthen has been participating in the experiment
since 1988. With a moderate extension of the telescope, Baikal will be
able to hold the leading position among all neutrino telescopes on the
Northern hemisphere. From approximately 2005 on, however, the the bigger
neutrino telescopes currently being constructed in the Mediterranean are
expected to take over.

Baikal
Group Home PageThe collaboration consists of Russian institutes (with
the INR Moscow, the Irkutsk State University, the Moscow State University
being the most prominent), and of DESY Zeuthen (Germany).

Image Courtesy of DESY Zeuthen

Image Courtesy of DESY Zeuthen

IceCube: A Next Generation Neutrino-Telescope

From the year 2004 on, IceCube, a high technology next
generation neutrino telescope, will be installed at the South Pole, several
thousands of meters below the surface of the Antarctic ice cap. With 4800
optical sensors distributed over a cubic kilometer of ice, IceCube will
be the biggest particle detector world-wide. At first, the South Pole appears
a strange site for deploying such an instrument. But there are crucial
advantages that outweigh the relative inaccessibility. The Polar ice being
more than 3 km deep and highly transparent is an ideal medium to detect
the faint light signals emitted by charged particles produced by high-energy
neutrinos. The necessary infrastructure on site is provided by the newly
renovated Amundsen-Scott station....

...IceCube will be about 30 times bigger and thus substantially
more sensitiv e than AMANDA. The deployment of all 4800 optical sensors
will be completed until 2010, but during the construction phase the deployed
parts of the detector will already produce high-quality data. The 677 optical
modules of AMANDA will be integrated into the the bigger IceCube array.
The schematic sketch shows the dimension of the two detectors. Just like
AMANDA, IceCube will be deployed in vertical strings. Each IceCube string
will comprise 60 optical modules (three times the number of modules attached
to the much shorter AMANDA strings), as well as their power-supply and
the cables for the signal readout. The modules at one string will be equally
spaced at a distance of 17 m. Each string will be lowered into a vertical
hole, drilled with pressurized hot water, such that the instrumented volume
of the detector spans a depth range between 1400 and 2400 m. A total of
80 holes will be drilled. They will be regularly distributed over a surface
of a square kilometer, the distance between two holes being 125 m.

IceTop is a km2 array of particle detectors that is
currently being installed at the south pole, right above the IceCube neutrino
telescope. It is used to detect extensive particle showers induced in our
atmosphere by high energy cosmic rays.

Its spacing (80 stations = 160 Cherenkov
ice tanks, 125m mean distance) allows the observation of cosmic rays with
energies between 1014eV and 1017eV. In this regime, the energy spectrum
is expected to include 2 kinks: The first, already observed by most experiments,
is at the energy where presumably light cosmic rays (protons) start to
be able to escape the magnetic fields of our galaxy and the observed fluxes
thus decrease faster above than below ("knee"). A second "knee" is expected
but yet unobserved for heavier particles like iron nuclei. Using IceCube
as a high energy neutrino detector and the CORSIKA air shower simulation
package, IceTop can identify the masses of primary cosmic ray particles
and unfold the energy spectra for different primaries.

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